Add the wasabi and Tamari (or soy sauce) to a small sauté pan and use a small whisk to blend until it’s smooth.
Place the pan over low-medium heat and add the butter. Swirl the pan around until the butter has melted and is completely incorporated.
Whisk in the honey and set aside to cool to room temperature.
While the glaze is cooling, cut the Ahi into small cubes, about 1-inch -- and season them with salt and pepper. (It's very easy to cut into cubes if it's semi-frozen. Just be sure they're thawed by the time you sear them.)
Coat the bottom of a medium-sized sauté pan with the oil and place it over high heat. Once the pan is very hot, add the Ahi and sear all but two opposing sides. (If you don't hear a sizzling sound when the tuna hits the pan, it's not hot enough -- wait for the sizzle!) Only cook it through a bit, less than ⅛-inch, probably no more than 10 seconds per side. You can use a fork to simply roll them to sear each side. You’ll want to remove them from the pan the instant they’re done, so doing this in small batches is a good idea. Place them directly on a plate or serving platter, raw side up. (You can also cut the tuna into strips, and slice them into cubes after searing them.)
Drizzle the cooled wasabi glaze over them, add toothpicks and serve.